I get asked to tune tunnel ram intakes fairly frequently,
and I think one reason, is many guys buy them with little or not much if any understanding of what that intake design was built to do,
but they like the "race LOOK" and want the "LOOK" and figure they can deal with the tuning issues, as they come up.
Id suggest you start by reading these linked threads,
keep in mind a tunnel ram intake is designed to run in the 3500 rpm-7000 plus rpm power band,
its an intake designed to maximize power and its generally not the best choice for a street car.
and that generally requires a cam with about a 240 @ .050 lift or greater duration, usually a reasonably tight 106-109 LSA,
open headers, at least 10.5:1 compression ratio,
and rear gears in the 3.73:1-4.56:1 range and a 3500 rpm stall speed or higher converter,
or a manual transmission to maximize the dual quad/tunnel ram intakes designed power curve potential.
yeah you can have a different basic combo, but the further you get from the design parameters,
the more difficult it becomes to tune and get it to run with a brisk crisp throttle responce, and no other issues.
and yes the larger the displacement , the higher the compression ratio, and closer the cam, duration,compression and exhaust header tune match
, the drive train gear ratios and the lighter the car is,
so the engine can maximize that intended upper rpm power band,
all the time the better that tunnel ram intake design, will tend to run.
many of the "problems" guys have running a tunnel ram intake have far less to do with the intake than the failure to operate it in its intended power band,
and match the other engine component selections to that power and rpm band for which it was designed.
https://pantera.infopop.cc/topic/individual-runner-carburetion
http://garage.grumpysperformance.co...-or-intake-is-too-restrictive.2994/#post-8394
USE THE CALCULATORS
http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
yes there have been numerous attempts to use dominator carbs on IR intake designs
none have yet proven really successful as most designed intake and carb combos,
provide excellent torque but tend to lack enough air flow for impressive peak rpm
OFFY AND WEIAND both sold IR tunnel ram intake designs , that allowed a specific dominator carb, where each venturi was set up to have its own individual idle and jetting etc.
to be used as an individual runner carb design, but BOTH also sold bolt on common plenums to increase the intakes upper rpm flow and power potential.
http://garage.grumpysperformance.com/index.php?threads/dual-quads.444/
http://garage.grumpysperformance.com/index.php?threads/holley-accelerator-pumps-cams.1790/
http://garage.grumpysperformance.com/index.php?threads/holley-annular-vs-down-leg-boosters.5229/
http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/
http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/
http://garage.grumpysperformance.com/index.php?threads/holley-carb-power-valves.1639/
http://garage.grumpysperformance.co...cedure-step-by-step-guide-with-pictures.5378/
http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/
keep in mind that just about anything you can do to make it easier to efficiently fill the engines cylinders will tend to increase efficiency and as a result power, the basic tunnel-ram style intake provides a very effective way to allow the fuel/air mix to enter the cylinder head ports with less flow restriction than most other intake manifold designs.
but theres almost always ways to reduce flow restriction and increase efficiency, most tunnel ram intakes are mass produced castings that will benefit from some careful port and runner clean-up work.
port matching would be an obvious first step, but plenum and runner mods can and usually do help power produced.
PORTING THE TUNNEL RAM INTAKE RUNNERS CAN AT TIMES PROVIDE VERY NOTICEABLE GAINS
keep in mind engine displacement, cam timing, compression ratio all effect the intake flow but its generally a taking the time and effort to match the cam timing , overlap and designed rpm range and well matched header and tuning the exhaust scavenging that will have the most noticeable effect and potential improvement on a tunnel rams flow characteristics
stock un-ported runner entrances of a stealth-ram intake base above
the same intake manifold design, lower runner entrance's after some runner entrance port work.
porting helps flow significantly
A properly set up and correctly tuned tunnel ram intake is designed to maximize an engines power band in the 5000-rpm-7500-rpm range on most v8 muscle car engines, its never going to be ideal cruising at below 5000-rpm but that does not mean it can't be used or that its going to be useless on a street driven muscle car, provided the owner knows how to adjust and tune it.
AND I'M ALMOST ALWAYS AMAZED AT THE COMPLETE MIS-MATCH OF PARTS, MOST GUYS ASSEMBLE THAT THEY THEN EXPECT TO RUN CORRECTLY.
and as usual, a bit of careful research into matching engine compression,
cylinder head, port cross sectional area,
runner length, cam timing, cam LSA,valve lift and duration,
head flow potential,collector length,
and exhaust header design,in general to inhance scavenging,
the cars gearing, carburator ,fuel/air ratio,fuel atomization, ignition advance curve,tire diameter, drive train gearing,etc.
to match the intended power band will go a long way towards getting any tuunnel ram intake to perform well
the most important and effective performance asset you have is simply your ability to ask yourself questions, the ability to think logically isolate and test components carefully and doing the research if its required to find the best answer's you'll need.
A well designed tunnel ram intake, with matching carburetors provides about the most direct, efficient ,strait line,path for the fuel/air mix, from carb to cylinder possible,only some of the individual runner stack injection intakes provide a more robust torque curve in the mid and upper rpm ranges, and once the engine operating rpm range or engine speed, cam timing and engine displacement, and exhaust scavenging components are well matched in an application, you can generally make exceptional power levels, but keep in mind the basic design requires you to get up into the 250-300 fps range for air flow inertia to become highly effective filling the cylinders.
the first issue most guys need to understand is that in most cases, both carbs will need to be jetted the same on all four corners and the opening synchronized so the fuel air mix is consistent before during and after the transition from idle to wide open throttle, and that your idle speed and quality of the idle will be dependent on your being able to read the plugs and determine whats going on in the combustion chamber.(this is rarely good for mileage or how the engine will run below about 4000rpm, but then the intake was and is designed primarily for operation above 4000rpm with little or no concern for its power curve or efficiency below that rpm level.
now I,m not suggesting a good tuner can,t make the car run reasonably well with a tunnel ram intake on the street,but its never going to be the ideal intake design on an engine loafing along below 3500rpm, 90% of the time ,especially if good throttle response and mileage are a primary goal. I can tell you from experience that the larger the displacement engines tend to be more tolerant of street use off that tunnel ram intake design, and gearing and cam timing and efficient header scavenging is critical to getting good results.
if the engine won,t idle you most likely have a vacuum leak or some fuel/air ratio issues or the timings off.
Yes you can tune a tunnel ram intake to make both good power and torque, in fact if the parts are correctly matched power from about 3500rpm-8000rpm will match or exceed most other choices, and a good tuner familiar with tuning a tunnel ram should be able to get the combo to run without a stumble or flat spots in the power curve.. because a tunnel ram intake by design has a strait shot at the back of the intake valve in the cylinder heads from the plenum with the least restriction to flow possible these intakes tend to make excellent upper mid rpm and peak power.
One factor thats frequently over looked is that most tunnel ram dual quad intakes have nearly identical runner dimensions and an almost direct strait line path from the carburetor s venturi to the back of the intake valve on each cylinder, (unlike most dual and single plane single carb intakes) which can easily be worth an extra 1%-3% in power due to reduced flow restriction I,ve frequently seen a 4%-8% % power gain from a properly tuned, dual quad tunnel ram intake over the best I could get from the single carb intake manifold designs, due to both the reduced flow restriction and better fuel/air ratio control between cylinders, but remember most tunnel ram intakes won,t produce those benefits until they operate in the designed rpm range which frequently starts at or above 4000rpm
keep in mind many EFI intakes are updated versions if the basic tunnel-ram intake design offering superior dry air flow and a direct injector shot of a high pressure mist of fuel aimed at the back of the intake valve
obviously you will need to carefully port match some intakes to some head ports due to the wide variation in sizes and shapes
PORT MATCHING THE INTAKE RUNNER EXIT TO THE CYLINDER HEAD PORT ENTRANCE USUALLY HELPS REDUCE RESTRICTIONS TO FLOW RATES, AND REDUCES FUEL/AIR DISTRIBUTION ISSUES
thats very useful info,
http://airdensityonline.com/free-calcs/
many guys fail to realize that only about 21% of the air content is oxygen thats physically useful in converting the fuels potential energy content into heat,
and rapidly expanding gases that produce the cylinder pressure that drives the piston down the cylinder, maintaining the ideal fuel to oxygen ratio will vary with altitude.
as a result the cost to run the car goes up and the cars power can go down.
another factor ignored is that not only does less dense air contain less oxygen it holds less MASS thus the inertia of the exhaust gasses exiting the headers has a bit less scavenging effect on the next incoming charge in the intake runner following it during overlap in cam timing
YOU MIGHT WANT TO ALSO READ THESE THREADS
http://garage.grumpysperformance.com/index.php?threads/options-on-dual-quads.11047/
http://garage.grumpysperformance.co...ical-constant-flow-injection.4502/#post-49562
http://www.superchevy.com/how-to/engines-drivetrain/sucp-0612-big-block-tunnel-ram-intake/
https://www.profilerperformance.com/216-bbc-tunnel-ram.html
http://www.jegs.com/p/Dart/Dart-Big-Block-Chevy-Tunnel-Ram-Intake-Manifolds/957642/10002/-1
summit racing has some package deals
http://www.summitracing.com/parts/sum-cwnd304
http://www.force-efi.com/machefi.htm
http://www.international-auto.com/fiat- ... gauges.cfm
http://mysite.verizon.net/vzezeqah/site ... ystems.pdf
yes you can run a tunnel ram intake with a small cam and small carburetors on the street, just for looks, yes they do make street tunnel rams with smaller runners that are designed to operate at lower rpms that the real race tunnel ram intake designs,and in that type of application you can set the carburetors to work progressively, but it won,t run ideally, youll loose a good deal of low and mid rpm torque and you'll never get near the benefits of the intake design, but yeah, it can be assembled and tuned to function, if your just into (THE LOOK)
lets go over the basics, most tunnel ram intakes are designed to operate efficiently in the 4000 rpm-8000 rpm power band, with TWO MATCHED 4 BARREL carburetors, they are race intake designs meant to maximize flow and minimize and port flow restrictions, and basically designed to be operated at wide open throttle most of the time, and use dual 4 barrel carburetors, so each carburetors venturie is effectively dropping its fuel/air mix into its own designated intake port, this mandates all four venturie,s should be jetted very similar and that the throttle blades on all four venturie,s in the carburetors open at approximately the same rate,and having two carburetors feed a single intake effectively reduces the vacuum signal each carburetors sees
,so power valves and jetting and accelerator pumps must compensate, that higher intended power band by default means that the engine must also have a cam with matching duration and LSA and heads designed to flow a fuel/air mix in the same basic power band,that will open the valves long enough and far enough to maximize the intake runner flow rates at that intended upper rpm power band, in most cases thats going to be somewhat dependent on engine displacement and compression but a good rule of thumb is a minimum of 10.5:1-13.5:1 compression and a cam with a 245-300 duration @ .050 lift to match the duration and resulting dynamic compression
to get a good even controllable fuel air ratio entering into each port , you ideally have two matched carburetors with 8 throttle bores located over the intake runner entrances with the jets flowing enough fuel to supply abut the ideal 12.6-13.0:1 fuel air ratio in that intended power band and intake runner cross sectional areas matched to the engines displacement and power band.
so you can,t just throw on two old quadra-jet carburetors, or vacuum secondary Holley,s and expect it to run correctly, now IM not saying it can run reasonably well if your skilled at tuning ,but it certainly will never reach its full potential with the mis-matched components.
if your setting the intake up to provide its maximum power potential the throttle linkage should open all the venturies at the same rate , and youll rarely be running the engine under 4000rpm, from the launch to the mph lights at the end of the strip
keep in mind a tunnel ram intake is designed to have an open carburetor venturie almost directly over each runner feeding that cylinder, and in most cases a small plenum to allow some small cross over so each intake runner has access to slightly more fuel/air mix than the single carb venturie supplying it alone can easily supply, theres usually a direct strait line shot from the back of the intake valve up thru the carb venturie, but the ideal flow requires high air and port speeds so the system works best well above about 4500rpm in most applications, and only if all 8 venturies flow equally, this is best accomplished when all eight venturies open equally and jetting, fuel pressure and accessories like power valves and boosters are consistent, because, maintaining equal fuel/air ratios, ie, fuel droplets or mist suspended in the air flow does not like rapid changes in direction of flow
I generally start with 7.5 power valves and #82 jets on all locations a 5.5 psi of fuel pressure then move up or down in jets or power valves as required, youll find it best to buy jets in these multi packs then re-place what you use
http://www.summitracing.com/parts/HLY-36-181/
BEFORE PORT/RUNNER CLEAN UP>>>>>>>>>>>>>>>>>>>>>>>>>>>>AFTER PORT/RUNNER CLEAN UP AND PORTING
two 450cfm Holley work reasonably well on a street car
http://www.summitracing.com/parts/CMB-03-0177/
two 600cfm Holley work reasonably well on a street/strip car
http://www.summitracing.com/parts/CMB-03-0183/?rtype=10
one reason a properly port matched tunnel ram intake flows efficiently is a strait path to the intake valve, in the cylinder head from the plenum
http://www.allcarbs.com/detail.php?pid= ... n=71&stt=0
two 1050 Holley dominators work reasonably well on a big block strip car
http://www.holley.com/0-9375-1.asp
http://www.profilerperformance.com/tunn ... v-216.html
calculate port size
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/lpv.php
http://www.73-87.com/7387garage/drivetrain/hei.htm
http://www.swartzracingmanifolds.com/tech/index.htm
RELATED INFO
http://www.hotrod.com/techarticles/carb ... index.html
INTERESTING RELATE ARTICLEs
http://www.superchevy.com/technical/eng ... index.html
http://www.carcraft.com/techarticles/03 ... index.html
http://www.holley.com/20-28.asp
http://www.holley.com/data/Products/Tec ... 9R8291.pdf
if your using two holley vacuum secondary carbs on the street.....this might prove useful
to try to maintain exactly even fuel distribution between runners...which will almost never happen if the carbs open in a totally non synchronized manor
BTW contact the cam manufacturer, as theres a thousand or more valid combos
but two cams Ive had very good results with recently when using the tunnel ram intake, design, are these,crane cams listed below, both were used in reasonably light weight cars with manual transmissions and cars with at least 11:1 cpr and 3.90:1-4.11"1 rear gearing, one was a 383,sbc the other was a 496bbc, youll obviously need to match tire diam. and gearing to match the engines power curve and keep the rpms in top gear reasonable as the car runs thru the lights at the end of the track.
bbc http://www.cranecams.com/product/cart.p ... il&p=24613
sbc http://www.cranecams.com/product/cart.p ... il&p=24572
and I think one reason, is many guys buy them with little or not much if any understanding of what that intake design was built to do,
but they like the "race LOOK" and want the "LOOK" and figure they can deal with the tuning issues, as they come up.
Id suggest you start by reading these linked threads,
keep in mind a tunnel ram intake is designed to run in the 3500 rpm-7000 plus rpm power band,
its an intake designed to maximize power and its generally not the best choice for a street car.
and that generally requires a cam with about a 240 @ .050 lift or greater duration, usually a reasonably tight 106-109 LSA,
open headers, at least 10.5:1 compression ratio,
and rear gears in the 3.73:1-4.56:1 range and a 3500 rpm stall speed or higher converter,
or a manual transmission to maximize the dual quad/tunnel ram intakes designed power curve potential.
yeah you can have a different basic combo, but the further you get from the design parameters,
the more difficult it becomes to tune and get it to run with a brisk crisp throttle responce, and no other issues.
and yes the larger the displacement , the higher the compression ratio, and closer the cam, duration,compression and exhaust header tune match
, the drive train gear ratios and the lighter the car is,
so the engine can maximize that intended upper rpm power band,
all the time the better that tunnel ram intake design, will tend to run.
many of the "problems" guys have running a tunnel ram intake have far less to do with the intake than the failure to operate it in its intended power band,
and match the other engine component selections to that power and rpm band for which it was designed.
https://pantera.infopop.cc/topic/individual-runner-carburetion
http://garage.grumpysperformance.co...-or-intake-is-too-restrictive.2994/#post-8394
- https://www.summitracing.com/parts/hly-0-9377-1/overview/
IR refers to INDIVIDUAL RUNNER ,
almost all tunnel rams are single plane intake designs with a small common plenum or two common plenums
USE THE CALCULATORS
http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
yes there have been numerous attempts to use dominator carbs on IR intake designs
none have yet proven really successful as most designed intake and carb combos,
provide excellent torque but tend to lack enough air flow for impressive peak rpm
OFFY AND WEIAND both sold IR tunnel ram intake designs , that allowed a specific dominator carb, where each venturi was set up to have its own individual idle and jetting etc.
to be used as an individual runner carb design, but BOTH also sold bolt on common plenums to increase the intakes upper rpm flow and power potential.
http://garage.grumpysperformance.com/index.php?threads/dual-quads.444/
http://garage.grumpysperformance.com/index.php?threads/holley-accelerator-pumps-cams.1790/
http://garage.grumpysperformance.com/index.php?threads/holley-annular-vs-down-leg-boosters.5229/
http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/
http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/
http://garage.grumpysperformance.com/index.php?threads/holley-carb-power-valves.1639/
http://garage.grumpysperformance.co...cedure-step-by-step-guide-with-pictures.5378/
http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/
keep in mind that just about anything you can do to make it easier to efficiently fill the engines cylinders will tend to increase efficiency and as a result power, the basic tunnel-ram style intake provides a very effective way to allow the fuel/air mix to enter the cylinder head ports with less flow restriction than most other intake manifold designs.
but theres almost always ways to reduce flow restriction and increase efficiency, most tunnel ram intakes are mass produced castings that will benefit from some careful port and runner clean-up work.
port matching would be an obvious first step, but plenum and runner mods can and usually do help power produced.
PORTING THE TUNNEL RAM INTAKE RUNNERS CAN AT TIMES PROVIDE VERY NOTICEABLE GAINS
keep in mind engine displacement, cam timing, compression ratio all effect the intake flow but its generally a taking the time and effort to match the cam timing , overlap and designed rpm range and well matched header and tuning the exhaust scavenging that will have the most noticeable effect and potential improvement on a tunnel rams flow characteristics
stock un-ported runner entrances of a stealth-ram intake base above
the same intake manifold design, lower runner entrance's after some runner entrance port work.
porting helps flow significantly
A properly set up and correctly tuned tunnel ram intake is designed to maximize an engines power band in the 5000-rpm-7500-rpm range on most v8 muscle car engines, its never going to be ideal cruising at below 5000-rpm but that does not mean it can't be used or that its going to be useless on a street driven muscle car, provided the owner knows how to adjust and tune it.
AND I'M ALMOST ALWAYS AMAZED AT THE COMPLETE MIS-MATCH OF PARTS, MOST GUYS ASSEMBLE THAT THEY THEN EXPECT TO RUN CORRECTLY.
and as usual, a bit of careful research into matching engine compression,
cylinder head, port cross sectional area,
runner length, cam timing, cam LSA,valve lift and duration,
head flow potential,collector length,
and exhaust header design,in general to inhance scavenging,
the cars gearing, carburator ,fuel/air ratio,fuel atomization, ignition advance curve,tire diameter, drive train gearing,etc.
to match the intended power band will go a long way towards getting any tuunnel ram intake to perform well
the most important and effective performance asset you have is simply your ability to ask yourself questions, the ability to think logically isolate and test components carefully and doing the research if its required to find the best answer's you'll need.
A well designed tunnel ram intake, with matching carburetors provides about the most direct, efficient ,strait line,path for the fuel/air mix, from carb to cylinder possible,only some of the individual runner stack injection intakes provide a more robust torque curve in the mid and upper rpm ranges, and once the engine operating rpm range or engine speed, cam timing and engine displacement, and exhaust scavenging components are well matched in an application, you can generally make exceptional power levels, but keep in mind the basic design requires you to get up into the 250-300 fps range for air flow inertia to become highly effective filling the cylinders.
the first issue most guys need to understand is that in most cases, both carbs will need to be jetted the same on all four corners and the opening synchronized so the fuel air mix is consistent before during and after the transition from idle to wide open throttle, and that your idle speed and quality of the idle will be dependent on your being able to read the plugs and determine whats going on in the combustion chamber.(this is rarely good for mileage or how the engine will run below about 4000rpm, but then the intake was and is designed primarily for operation above 4000rpm with little or no concern for its power curve or efficiency below that rpm level.
now I,m not suggesting a good tuner can,t make the car run reasonably well with a tunnel ram intake on the street,but its never going to be the ideal intake design on an engine loafing along below 3500rpm, 90% of the time ,especially if good throttle response and mileage are a primary goal. I can tell you from experience that the larger the displacement engines tend to be more tolerant of street use off that tunnel ram intake design, and gearing and cam timing and efficient header scavenging is critical to getting good results.
if the engine won,t idle you most likely have a vacuum leak or some fuel/air ratio issues or the timings off.
Yes you can tune a tunnel ram intake to make both good power and torque, in fact if the parts are correctly matched power from about 3500rpm-8000rpm will match or exceed most other choices, and a good tuner familiar with tuning a tunnel ram should be able to get the combo to run without a stumble or flat spots in the power curve.. because a tunnel ram intake by design has a strait shot at the back of the intake valve in the cylinder heads from the plenum with the least restriction to flow possible these intakes tend to make excellent upper mid rpm and peak power.
One factor thats frequently over looked is that most tunnel ram dual quad intakes have nearly identical runner dimensions and an almost direct strait line path from the carburetor s venturi to the back of the intake valve on each cylinder, (unlike most dual and single plane single carb intakes) which can easily be worth an extra 1%-3% in power due to reduced flow restriction I,ve frequently seen a 4%-8% % power gain from a properly tuned, dual quad tunnel ram intake over the best I could get from the single carb intake manifold designs, due to both the reduced flow restriction and better fuel/air ratio control between cylinders, but remember most tunnel ram intakes won,t produce those benefits until they operate in the designed rpm range which frequently starts at or above 4000rpm
keep in mind many EFI intakes are updated versions if the basic tunnel-ram intake design offering superior dry air flow and a direct injector shot of a high pressure mist of fuel aimed at the back of the intake valve
obviously you will need to carefully port match some intakes to some head ports due to the wide variation in sizes and shapes
PORT MATCHING THE INTAKE RUNNER EXIT TO THE CYLINDER HEAD PORT ENTRANCE USUALLY HELPS REDUCE RESTRICTIONS TO FLOW RATES, AND REDUCES FUEL/AIR DISTRIBUTION ISSUES
thats very useful info,
http://airdensityonline.com/free-calcs/
many guys fail to realize that only about 21% of the air content is oxygen thats physically useful in converting the fuels potential energy content into heat,
and rapidly expanding gases that produce the cylinder pressure that drives the piston down the cylinder, maintaining the ideal fuel to oxygen ratio will vary with altitude.
as a result the cost to run the car goes up and the cars power can go down.
another factor ignored is that not only does less dense air contain less oxygen it holds less MASS thus the inertia of the exhaust gasses exiting the headers has a bit less scavenging effect on the next incoming charge in the intake runner following it during overlap in cam timing
YOU MIGHT WANT TO ALSO READ THESE THREADS
http://garage.grumpysperformance.com/index.php?threads/options-on-dual-quads.11047/
http://garage.grumpysperformance.co...ical-constant-flow-injection.4502/#post-49562
http://www.superchevy.com/how-to/engines-drivetrain/sucp-0612-big-block-tunnel-ram-intake/
https://www.profilerperformance.com/216-bbc-tunnel-ram.html
http://www.jegs.com/p/Dart/Dart-Big-Block-Chevy-Tunnel-Ram-Intake-Manifolds/957642/10002/-1
summit racing has some package deals
http://www.summitracing.com/parts/sum-cwnd304
http://www.force-efi.com/machefi.htm
http://www.international-auto.com/fiat- ... gauges.cfm
http://mysite.verizon.net/vzezeqah/site ... ystems.pdf
yes you can run a tunnel ram intake with a small cam and small carburetors on the street, just for looks, yes they do make street tunnel rams with smaller runners that are designed to operate at lower rpms that the real race tunnel ram intake designs,and in that type of application you can set the carburetors to work progressively, but it won,t run ideally, youll loose a good deal of low and mid rpm torque and you'll never get near the benefits of the intake design, but yeah, it can be assembled and tuned to function, if your just into (THE LOOK)
lets go over the basics, most tunnel ram intakes are designed to operate efficiently in the 4000 rpm-8000 rpm power band, with TWO MATCHED 4 BARREL carburetors, they are race intake designs meant to maximize flow and minimize and port flow restrictions, and basically designed to be operated at wide open throttle most of the time, and use dual 4 barrel carburetors, so each carburetors venturie is effectively dropping its fuel/air mix into its own designated intake port, this mandates all four venturie,s should be jetted very similar and that the throttle blades on all four venturie,s in the carburetors open at approximately the same rate,and having two carburetors feed a single intake effectively reduces the vacuum signal each carburetors sees
,so power valves and jetting and accelerator pumps must compensate, that higher intended power band by default means that the engine must also have a cam with matching duration and LSA and heads designed to flow a fuel/air mix in the same basic power band,that will open the valves long enough and far enough to maximize the intake runner flow rates at that intended upper rpm power band, in most cases thats going to be somewhat dependent on engine displacement and compression but a good rule of thumb is a minimum of 10.5:1-13.5:1 compression and a cam with a 245-300 duration @ .050 lift to match the duration and resulting dynamic compression
to get a good even controllable fuel air ratio entering into each port , you ideally have two matched carburetors with 8 throttle bores located over the intake runner entrances with the jets flowing enough fuel to supply abut the ideal 12.6-13.0:1 fuel air ratio in that intended power band and intake runner cross sectional areas matched to the engines displacement and power band.
so you can,t just throw on two old quadra-jet carburetors, or vacuum secondary Holley,s and expect it to run correctly, now IM not saying it can run reasonably well if your skilled at tuning ,but it certainly will never reach its full potential with the mis-matched components.
if your setting the intake up to provide its maximum power potential the throttle linkage should open all the venturies at the same rate , and youll rarely be running the engine under 4000rpm, from the launch to the mph lights at the end of the strip
keep in mind a tunnel ram intake is designed to have an open carburetor venturie almost directly over each runner feeding that cylinder, and in most cases a small plenum to allow some small cross over so each intake runner has access to slightly more fuel/air mix than the single carb venturie supplying it alone can easily supply, theres usually a direct strait line shot from the back of the intake valve up thru the carb venturie, but the ideal flow requires high air and port speeds so the system works best well above about 4500rpm in most applications, and only if all 8 venturies flow equally, this is best accomplished when all eight venturies open equally and jetting, fuel pressure and accessories like power valves and boosters are consistent, because, maintaining equal fuel/air ratios, ie, fuel droplets or mist suspended in the air flow does not like rapid changes in direction of flow
I generally start with 7.5 power valves and #82 jets on all locations a 5.5 psi of fuel pressure then move up or down in jets or power valves as required, youll find it best to buy jets in these multi packs then re-place what you use
http://www.summitracing.com/parts/HLY-36-181/
BEFORE PORT/RUNNER CLEAN UP>>>>>>>>>>>>>>>>>>>>>>>>>>>>AFTER PORT/RUNNER CLEAN UP AND PORTING
two 450cfm Holley work reasonably well on a street car
http://www.summitracing.com/parts/CMB-03-0177/
two 600cfm Holley work reasonably well on a street/strip car
http://www.summitracing.com/parts/CMB-03-0183/?rtype=10
one reason a properly port matched tunnel ram intake flows efficiently is a strait path to the intake valve, in the cylinder head from the plenum
http://www.allcarbs.com/detail.php?pid= ... n=71&stt=0
two 1050 Holley dominators work reasonably well on a big block strip car
http://www.holley.com/0-9375-1.asp
http://www.profilerperformance.com/tunn ... v-216.html
calculate port size
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/lpv.php
http://www.73-87.com/7387garage/drivetrain/hei.htm
http://www.swartzracingmanifolds.com/tech/index.htm
RELATED INFO
http://www.hotrod.com/techarticles/carb ... index.html
INTERESTING RELATE ARTICLEs
http://www.superchevy.com/technical/eng ... index.html
http://www.carcraft.com/techarticles/03 ... index.html
http://www.holley.com/20-28.asp
http://www.holley.com/data/Products/Tec ... 9R8291.pdf
if your using two holley vacuum secondary carbs on the street.....this might prove useful
to try to maintain exactly even fuel distribution between runners...which will almost never happen if the carbs open in a totally non synchronized manor
BTW contact the cam manufacturer, as theres a thousand or more valid combos
but two cams Ive had very good results with recently when using the tunnel ram intake, design, are these,crane cams listed below, both were used in reasonably light weight cars with manual transmissions and cars with at least 11:1 cpr and 3.90:1-4.11"1 rear gearing, one was a 383,sbc the other was a 496bbc, youll obviously need to match tire diam. and gearing to match the engines power curve and keep the rpms in top gear reasonable as the car runs thru the lights at the end of the track.
bbc http://www.cranecams.com/product/cart.p ... il&p=24613
sbc http://www.cranecams.com/product/cart.p ... il&p=24572
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